1. Field of the Invention
The invention relates in general to the field of data networking and communications, and in particular to interconnecting computers to a local area network (xe2x80x9cLANxe2x80x9d) or a wide area network (xe2x80x9cWANxe2x80x9d) through data lines that also carry power.
2. Description of the Related Art
Network devices typically communicate via wired data lines and receive power from a separate line. For example, personal computers (xe2x80x9cPCsxe2x80x9d) may communicate Ethernet signals via category three (CAT-3) or category five (CAT-5) twisted pair wire and receive power from a second cable connected to a power source, such as a wall socket or a battery. However, it is desirable to be able to eliminate the need for the second cable. The following describes examples of network devices that benefit from the elimination of the separate power line, and then describes some of the inadequacies of previous solutions.
Plain old telephone service (xe2x80x9cPOTSxe2x80x9d) combines a voice signal with a power signal. The combined signal is transmitted over twisted pair cable between the telephone and the line card at the public telephone exchange office. The line card also supplies power over the two wires carrying the voice signal. However, the voice signal supported by POTS is not sufficient for bandwidth intensive communications needs, such as, Ethernet communications. Similarly, ISDN communications transmit power and digital data between an ISDN modem and a telephone switch. However, ISDN data rates are more than an order of magnitude lower than Ethernet data rates.
Wireless network adapters can interconnect PCs, or other networked device. The wireless network adaptors use, for example, infrared (IR) or radio frequency (RF) modulation to transmit data between wireless access points and the wireless adaptors connected to PCs. Although the wireless adaptors and wireless access points may be more expensive than comparable wired equipment, they provide savings in wiring costs and permit greater flexibility by allowing the PCs to be moved to any location within the range of the system without the necessity of rewiring the building.
Typically, a transceiver (meaning transmitter and receiver) called a wireless access point, mounted at an elevated location, such as on a ceiling or high on a wall, provides network data communications between a network hub, switch, router or server, to all the PCs located in that room which are equipped with a compatible wireless networking adaptor. The wireless access point is an active electronic device that requires a communications link to a hub or server as well as electrical power to operate. Both the data signal and power signal must be provided to the wireless access point. The data signal is typically at a lower voltage than the power signal, but at a significantly higher frequency, sufficient to sustain a high data transfer rate (e.g., 100 kilobits per second or higher). The available power is usually 110V or 220V AC at frequencies below one hundred Hz. Often two separate sets of wires are used to carry the data signal and power signal. One set of wires is used to couple the wireless access point and the hub and the other set of wires is used to couple the wireless access point to the power outlet.
Eliminating the need for separate power and data wiring simplifies the installation of a wireless access point and can reduce the cost of the installation. Therefore, it is desirable to transmit sufficient electrical power to operate the wireless access point through the network cable that is used to connect the wireless access point to the hub or server.
One possible solution is to transmit power on the unused wires of the data cable. An example of this approach can be found in the VIPSLAN-10(trademark) product manufactured by the JVC Information Products Company of Irvine, Calif. Of course this requires that additional, unused wire pairs be available in the data cable, which may not always be available. Also, if a change in the networking standard in the future dictates the use of the currently unused wire pairs in the networking cable, this solution becomes difficult to implement.
Therefore, what is needed is a solution that reduces the wiring requirements to transmit data and power to a wireless access point without having to use additional wire pairs.
One embodiment of the invention includes an apparatus for providing electric power supply current to a network device across a transmission line. A power and data coupler (xe2x80x9cthe couplerxe2x80x9d) is coupled to one end of the transmission line. The transmission line is also adapted for transmission of a data signal. The coupler has a data input and a power input. Power supply current from the power input is coupled to data signal from the data input and the combined power supply current and data signal is coupled to one end of the transmission line. The opposite end of the transmission line is coupled to a power and data decoupler (xe2x80x9cthe decouplerxe2x80x9d). The decoupler has a power output and a data output. Both the data output and power output of the decoupler are coupled to the network device. The combined power supply current and data signal is decoupled by the decoupler, and the data signal is supplied to the data output and the power supply current is supplied to the power output. Thus, the data signal and the power supply current are coupled and transmitted via the transmission line from the coupler to the decoupler and then decoupled and provided separately to the network device.
In another embodiment, the transmission line includes two transmission lines. One of the transmission lines carries both data and power signals.
In other embodiments, the power signal includes alternating current and/or direct current.
In another embodiment, the transmission lines include twisted pair cables.
In other embodiments, the network devices include wireless access points, network interface cards, peripheral devices and/or network computers.
These features of the invention will be apparent from the following description which should be read in light of the accompanying drawings.